This invention relates to a circuit board connector mounted on a circuit board, as well as to an electric device using this connector.
Various circuit board connectors for being mounted on printed circuit boards are known in the art. A connector of this type has a male connector portion constituted by a plurality of connector pins provided on a printed circuit board, and a female connector portion for achieving electrical contact and connection with the male connector portion. The female connector portion is additionally so adapted that it will not become disconnected inadvertently from the male connector portion. These two connector portions constitute one set. Circuit board connectors of this kind may be classified broadly into straight-type connectors and edge-type connectors. In straight-type connectors, the connector pins are provided on the mounting surface of the circuit board in a substantially upstanding attitude. In the edge-type connectors, the connector pins are bent at a right angle at a point along their length so as to be made substantially parallel to the mounting surface of the circuit board.
A conventional straight-type connector for a circuit board will be described in brief with reference to the drawings. FIG. 1 is a side view illustrating a circuit board connector according to the prior art. As shown in FIG. 1, the connector has a male connector portion 100 and a female connector portion 102 forming one set. The female connector portion 102 internally incorporates a connector terminal 106 (indicated by the broken lines) to which a solid wire 104 or flat cable (not shown) is connected. The connector terminal 106 has a resilient portion which, when a connector pin 108 is inserted into it, undergoes elastic deformation so as to produce a retaining force by which the connector terminal 106 and connector pin 108 are joined together to assure an electrical connection between them.
Through a method in which the male connector portion 100 is insert-molded with or press-fitted into a block body 110 consisting of synthetic resin, the connector pin 108 is attached so as to assume an upright attitude on the mounting surface of a circuit board 112. After an end portion 108a of the connector pin 108 is passed through a land hole of a circuit pattern formed on the surface of the circuit board 112, solder 114 is formed on each connector pin 108 by a soldering device or the like. As a result, the male connector portion 100 is mechanically and electrically joined to the circuit board 112.
By attaching the female connector portion 102 to or detaching it from the male connector portion 100 thus joined to the circuit board 112, the circuit board 112 is connected to or disconnected from an external electric circuit.
In actual use, the circuit board 112 is exposed to conditions over a wide temperature range (e.g., -10.degree. C..about.85.degree. C.). Consequently, in the prior-art connector of the kind described above, the block body 110 constituting the male connector portion 100 expands or contracts owing to change in the ambient temperature. This is accompanied by a change in the spacing between the connector pins 108, as a result of which the spacing between the connector pins 108 may no longer match the spacing between the land holes of the circuit board 112. In actuality, the circuit board 112 also expands or contracts in the same direction as the block body 110 so that the magnitude of the offset between the pins 108 and land holes is somewhat mitigated. However, since the material constituting the block body 110 and the material constituting the circuit board 112 have different thermal conductivities, a discrepancy always develops between the spacing of the connector pins 108 and the spacing of the land holes in the circuit board 112. This discrepancy in spacing causes stress to develop in the solder 114.
Further, when the connector pin 108 is soldered to the circuit board 112, the hardening of the solder 114 gives rise to a difference in thermal shrinkage between the block body 110 and circuit board 112. This difference in thermal shrinkage also causes residual stress in the solder 114. This stress produced in the solder 114 can cause the solder to crack, as shown in FIG. 2, or can cause the circuit pattern to peel off. When the solder cracks or the circuit pattern peels off, this can cause a break in a signal line of an electric circuit and result in an accident or malfunction.
Recent reductions in the size of electric devices and an increase in the mounting density of electric and electronic parts have been accompanied by a change in the shapes of connectors on circuit boards. For example, in a case where a connector having a plurality of connector pins is mounted on a circuit board, generally the plurality of connector pins are arrayed in a single straight row. In recent years, however, cases have arisen in which the connector pins must be arrayed irregularly and not linearly.
When the plurality of connector pins are attached to one block body in the above-mentioned case in which the connector pins are arrayed irregularly, instances arise in which the connector pins do not fit into the land holes smoothly owing to an error in the spacing between the connector pins and an error in the spacing between the land holes of the circuit board. If the connector pins are forcibly pushed into the land holes under such circumstances, the connector pins develop residual stress that tends to spread the pins apart or force them closer together, as a result of which the solder tends to crack. Consequently, in a case where the connector pins must be arrayed irregularly, the arrangement adopted in the prior art is one in which mutually independent connectors 116 are fitted into a circuit board 118 one at a time, as illustrated in FIG. 3. However, if the connectors 116 are thus mounted one at a time, it is easy to make mistakes when inserting the connector pins. Accordingly, it is necessary to take great care when the connectors 116 are mounted on the circuit board, and the operation involved is highly inefficient.
Besides cases in which connector pins are arrayed irregularly on the same plane, there are also cases in which connector pins are arrayed on two circuit boards not located on the same plane. For example, FIG. 4 illustrates a side section of a word processor. Here a CRT, two circuit boards 122A, 122B and a power supply 114 are accommodated within a case 120 of the word processor. It is necessary for the two circuit boards 122A, 122B to be electrically interconnected, and it is also required for the circuit boards to be connected to the power supply 114. In such cases also, a variance in the difference in the levels of the circuit boards, a variance in the spacing of the circuit boards and a variance in the dimensions of the block body of the connector cause residual stress to act upon the connector pins when the connectors are joined. Consequently, it is still necessary to separate the connectors one at a time and the aforesaid problem still arises, namely the fact that errors tend to occur when inserting the connector pins.